Throughout the world, emergency services have been the subject of widespread standardization for many years. Telephone subscribers in particular have benefited from such standardization via the establishment of Emergency Services Notification (ESN) systems. Within North America, the prevalent ESN system is standardized on the dial sequence 911. Still other jurisdictions have selected a diversity of alternative sequences, although the purpose of each ESN system is to quickly and reliably call for assistance when an emergency occurs. Telephone users may therefore call for any type of emergency assistance by dialing the ESN telephone number from within the geographic area served by the ESN system. In order for this service to be available, the Public Switched Telephone Network (PSTN) supplier in the area must route all such calls to an appropriate call answering center. Such call answering centers are often municipal offices such as a police department dispatch.
Original ESN systems simply detected the ESN dialing sequence (e.g., 911) and routed the emergency telephone call to a special answering point. No subscriber information or high-priority call handling was included in these earlier ESN systems. However, many ESN system operators quickly realized that the most critical information required of the caller was his or her location. Under such ESN systems, there was no way to quickly dispatch assistance when the nature of the emergency precluded passing that information to the answering point,
Many jurisdictions have since installed enhanced systems that include technologies for reporting the calling party's Directory Number (DN) directly to the call answering center which are typically referred to as a Public Safety Answering Point (PSAP). Via a mechanism known as Automatic Number Identification/Automatic Location Identification (ANI/ALI), whereby DN information is cross-referenced to a location database that identifies the geographical location of the calling party requiring assistance. ANI/ALI is a mechanism that aligns a specific telephone DN to a physical resource such as a port or connection. The physical resource is then cross-referenced to the geographical location data or civic address. Thus, the ANI/ALI mechanism is used to determine which PSAP has jurisdiction by cross-referencing the civic address to the responsible agency whereby the DN information is used by the PSAP to dispatch the emergency services crew to the caller's location.
Accuracy of the location database depends on a consistent and rigorously applied Civic Addressing System (CAS) to supply a unique address for each possible originating telephone number. In reality, the CAS is often inaccurate. This is especially true in situations involving users that cannot effectively participate in the ESN system due to their Private Branch Exchange (PBX) telephone systems having no practical way to report location information to the PSTN. For example, a commercial, industrial, educational, or governmental institution may have hundreds of telephony devices located in various buildings over a wide geographic area, and yet a “911 call” from any of them may identify only one location.
Moreover, existing ANI/ALI mechanisms typically depend upon a one-to-one correspondence of a physical resource to each DN entry. As suggested above in regard to PBX telephone systems, the basic emergency function of any such ESN system fails when multiple DN entries are associated with a single resource such as a phone system element such as a PBX acting as a concentrator for multiple telephone instruments to telephone trunk circuits. The emergence of Internet Protocol (IP) based telephony has further exacerbated the ANI/ALI issue within ESN systems. IP telephony uses a packet switched architecture that allows users to share the communications resource in an efficient manner via Voice over IP (VoIP) technology. As in the PBX scenario, the sharing of a physical channel by a VoIP device means there is no one-to-one correspondence of a physical resource to a DN entry. Accordingly, ESN system failure is also present within situations where the calling party uses a VoIP device to place the emergency services call. In such instances, a single DN entry may be associated with a single resource such as the VoIP telephony, but the nature of VoIP telephony often precludes accurate identification of the geographic location of the user in need of emergency assistance.
IP telephony providers have adopted a number of stopgap measures to provide a semblance of reliability to ESN systems. Most often, such IP telephony providers simply require their customers to read and agree to a liability waiver which describes the ESN system as based on the address that the customer provides on sign-up for the VoIP service. This method depends on: (a) the accuracy of the address as reported by the user; (b) a static user; and, (c) co-operation of the ESN system's PSAP. This latter issue is problematic because many jurisdictions have legislation precluding any auto-dialer mechanism to place an ESN call. IP telephony providers therefore often use call centers for handling emergency calls.
IP telephony provider call centers function such that an emergency call placed on the VoIP service is redirected to the call center where a human operator ascertains the nature of the call and whether the caller is located at the reported address. The human operator at the call center then forwards the emergency call to a predesignated PSAP. However, often such emergency calls are forwarded from the IP telephony provider's call center and sent to an administrative, supervisor, or general purpose telephone line where the answering party is not a trained ESN call-taker. With no presumed urgency associated with the line, emergency calls may ring many times before being answered or may not be answered at all. Even after being answered, the situation must be explained to the answering party before it is forwarded to a call taker in the PSAP.
Another known stopgap solution involves maintaining a traditional telephone service line at each user's location. A device is used to sense the dialing of the ESN dialing sequence by a VoIP device. The VoIP device then goes off line and dials the ESN dialing sequence on the traditional telephone circuit—e.g., a plain old telephone service (POTS) line. The IP-based audio is then routed to the PSAP via the POTS line connection. This solution is less than desirable because it requires the traditional circuit just to maintain the location capabilities of the ESN system.
As mentioned above, the inherent nature of VoIP telephony often precludes accurate identification of the geographic location of the user in need of emergency assistance. One of the significant advantages of IP telephony is the ability for a mobile user to receive “dial tone” from their home location regardless of where the mobile user might be located worldwide. This mobility, when tied with the advanced services granted by IP telephony, provides a powerful motivator for both business and personal users to adopt the new technology. However, IP telephony mobility often confounds the stopgap measures put into place by the IP telephony providers to address ESN system concerns. Although efforts are being undertaken to try to trace the VoIP user's location through the network, there have been inherent difficulties due to the changeability of the worldwide IP network including diverse security measures to overcome sophisticated spoofing and other attacks aimed at disrupting normal network operations.
As traditional telephone circuits continue to give way to advanced IP-based technologies, the public's confidence in ESN systems will be diminished unless the problematic aspects discussed above are resolved. The ideal solution will enable the existing PSAP architectures to be maintained and enhanced. Moreover, the emergence of IP telephony, including specifically VoIP, as a mainstream communications method for use by members of the public at their residences has highlighted the need for such services to implement effective ESN system services (e.g., 911 services). Without an effective method to implement ESN services, it is likely that the various national communications authorities who are ultimately responsible for ESN notification within their given jurisdictions not will allow the widespread implementation of IP telephony. There exists, therefore, a need to supplement existing emergency response tools within the context of VoIP technologies to more effectively direct emergency responders to an actual emergency location.